Re: optimisation for a table with frequently used query

[Lew <lew(at)nospam(dot)lewscanon(dot)com>]

danmcb wrote:
> > SELECT * from my_table where id_1 = x and id_2 = y;
> > Neither id_1 or id_2 or the combination of them is unique. I expect
> > this table to become large over time.

PFC wrote:
> Create an index on (id_1, id_2), or (id_2,id_1).

What are the strengths and weaknesses compared to creating two indexes, one on 
each column?

I am guessing that changes to the table are slower with two indexes.  How 
could it affect queries?

What if the typical query pattern was more balanced among constraints on one 
column, on the other, and on both?

--
Lew